when business obtains a CC line of say 30,000

do you show this on your books as capital that may be used?

A credit line is not capital until it is exercized.

I.E. On the balance sheet it shows up once you pull 30,000 and place it into an account / asset. The credit of 30,000 into the account is offset by the 30,000 debit added to the liabilities section.